But there seems to be a fascination with Middleton's wardrobe that exceeds all other celebrities — so much so, the purchases might've added over $1.4 billion to the U.K. fashion industry.

And it's not just her wardrobe. In 2011, a spokesperson for a U.K. jewelry company told Vogue that sales of sapphire and diamond rings — similar to the engagement ring Prince William gave Middleton — had increased 30 percent since the couple made the announcement.

As for the most recent example of "The Kate Effect"? The Indian designer told The Wall Street Journal her company is increasing production of the dress by 500 percent to meet the growing demand.